240 research outputs found
Non-KPZ modes in two-species driven diffusive systems
Using mode coupling theory and dynamical Monte-Carlo simulations we
investigate the scaling behaviour of the dynamical structure function of a
two-species asymmetric simple exclusion process, consisting of two coupled
single-lane asymmetric simple exclusion processes. We demonstrate the
appearence of a superdiffusive mode with dynamical exponent in the
density fluctuations, along with a KPZ mode with and argue that this
phenomenon is generic for short-ranged driven diffusive systems with more than
one conserved density. When the dynamics is symmetric under the interchange of
the two lanes a diffusive mode with appears instead of the non-KPZ
superdiffusive mode.Comment: 5 pages, 7 figure
Fibonacci family of dynamical universality classes
Universality is a well-established central concept of equilibrium physics.
However, in systems far away from equilibrium a deeper understanding of its
underlying principles is still lacking. Up to now, a few classes have been
identified. Besides the diffusive universality class with dynamical exponent
another prominent example is the superdiffusive Kardar-Parisi-Zhang (KPZ)
class with . It appears e.g. in low-dimensional dynamical phenomena far
from thermal equilibrium which exhibit some conservation law. Here we show that
both classes are only part of an infinite discrete family of non-equilibrium
universality classes. Remarkably their dynamical exponents are given
by ratios of neighbouring Fibonacci numbers, starting with either (if
a KPZ mode exist) or (if a diffusive mode is present). If neither a
diffusive nor a KPZ mode are present, all dynamical modes have the Golden Mean
as dynamical exponent. The universal scaling functions of
these Fibonacci modes are asymmetric L\'evy distributions which are completely
fixed by the macroscopic current-density relation and compressibility matrix of
the system and hence accessible to experimental measurement.Comment: 8 pages, 5 Figs (2 Figure revised, one new Figure added), revised
introductio
Exact scaling solution of the mode coupling equations for non-linear fluctuating hydrodynamics in one dimension
We obtain the exact solution of the one-loop mode-coupling equations for the
dynamical structure function in the framework of non-linear fluctuating
hydrodynamics in one space dimension for the strictly hyperbolic case where all
characteristic velocities are different. All solutions are characterized by
dynamical exponents which are Kepler ratios of consecutive Fibonacci numbers,
which includes the golden mean as a limiting case. The scaling form of all
higher Fibonacci modes are asymmetric L\'evy-distributions. Thus a hierarchy of
new dynamical universality classes is established. We also compute the precise
numerical value of the Pr\"ahofer-Spohn scaling constant to which scaling
functions obtained from mode coupling theory are sensitive.Comment: PACS classification: \pacs{05.60.Cd, 05.20.Jj, 05.70.Ln, 47.10.-g
Understanding the Motives for Terrorism - Does it Have an Effect on Psychological Reactions? A Replication and Extension
The collective communication model of terrorism (CCMT) proposes that understanding terrorists' motives influences appraisal (threat perception and emotional well-being) and reaction to terrorism (intention to retaliate). Fischer et al. (2011) presented evidence from two experiments for the assumption that understanding motives of terrorism influences appraisal. The present preregistered experiment aimed to replicate their second experiment, validate the measures they used, and also test the second proposition of the CCMT. Ensuring sufficient power for multiple tests and the given effect size, we collected data from 188 participants. The findings by Fischer et al. (2011) were partly replicated, but the comparison of the original effect sizes and the effect sizes from the replication attempt does not provide convincing evidence for the hypothesis that understanding the motives for terrorism reduces the perceived threat or negative emotional impact of acts of terrorism. Correlations with other risk-perception measures call into question the validity of the items used to assess perceived threat. Results suggest that understanding the motives for terrorism may influence whether the targeted populations want to retaliate
Ensemble-induced strong light-matter coupling of a single quantum emitter
We discuss a technique to strongly couple a single target quantum emitter to
a cavity mode, which is enabled by virtual excitations of a nearby mesoscopic
ensemble of emitters. A collective coupling of the latter to both the cavity
and the target emitter induces strong photon non-linearities in addition to
polariton formation, in contrast to common schemes for ensemble strong
coupling. We demonstrate that strong coupling at the level of a single emitter
can be engineered via coherent and dissipative dipolar interactions with the
ensemble, and provide realistic parameters for a possible implementation with
SiV defects in diamond. Our scheme can find applications, amongst others,
in quantum information processing or in the field of cavity-assisted quantum
chemistry.Comment: 13 pages, 6 figures; substantially revised manuscript; see
arXiv:1912.12703 for mathematical derivation
Cavity-assisted mesoscopic transport of fermions: Coherent and dissipative dynamics
We study the interplay between charge transport and light-matter interactions
in a confined geometry, by considering an open, mesoscopic chain of two-orbital
systems resonantly coupled to a single bosonic mode close to its vacuum state.
We introduce and benchmark different methods based on self-consistent solutions
of non-equilibrium Green's functions and numerical simulations of the quantum
master equation, and derive both analytical and numerical results. It is shown
that in the dissipative regime where the cavity photon decay rate is the
largest parameter, the light-matter coupling is responsible for a steady-state
current enhancement scaling with the cooperativity parameter. We further
identify different regimes of interest depending on the ratio between the
cavity decay rate and the electronic bandwidth. Considering the situation where
the lower band has a vanishing bandwidth, we show that for a high-finesse
cavity, the properties of the resonant Bloch state in the upper band are
transfered to the lower one, giving rise to a delocalized state along the
chain. Conversely, in the dissipative regime with low cavity quality factors,
we find that the current enhancement is due to a collective decay of
populations from the upper to the lower band.Comment: 52 pages, 11 figure
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Correcting for the missing rich: An application to Wealth Survey Data
It is a well-known criticism that if the distribution of wealth is highly concentrated, survey data are hardly reliable when it comes to analyzing the richest parts of society. This paper addresses this criticism by providing a general rationale of the underlying methodological problem as well as by proposing a specific methodological approach tailored to correcting the arising bias. We illustrate the latter approach by using Austrian data from the Household Finance and Consumption Survey. Specifically, we identify suitable parameter combinations by using a series of maximum-likelihood estimates and appropriate goodness-of-fit tests to avoid arbitrariness with respect to the fitting of the Pareto distribution. Our results suggest that the alleged non-observation bias is considerable, accounting for about one quarter of total net wealth in the case of Austria. The method developed in this paper can easily be applied to other countries where survey data on wealth are available
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